The present invention relates to an ink-dot printer which comprises a pair of slit forming members arranged so as to define a slit therebetween, ink storage means for storing ink so that the slit between the two slit forming member is immersed in the ink, a recording medium opposed to the slit, a needle movable between a rest position in which the distal end portion of the needle facing the recording medium is located in the slit and a projected position in which the distal end portion is projected from the slit to be located closer to the recording medium than in the rest position, driving means for moving the needle between the rest position and the projected position, and ink attracting means for generating a magnetic or electric field in the slit between the two slit forming members, thereby attracting the ink from the ink storage means into the slit to cause the ink to attach to the distal end portion of the needle located in the rest position, so that the ink is moved to the recording medium to form an ink dot thereon as the needle attaching the ink on the distal end portion thereof in the rest position moves to approach the recording medium in the projected position.
In the prior art ink-dot printers with the construction described above, if a magnetic field is to be produced to attract the ink into the slit between the slit forming members, the slit forming members are coupled to an electromagnet, and magnetic ink is used for the ink.
In the conventional printers of this type, moreover, if an electric field is to be produced to attract the ink into the slit between the slit forming members, the slit forming members are connected to a power source, and oil ink is used for the ink.
In these conventional ink-dot printers, electric power comsumption required for the production of an ink attracting magnetic or electric field having such strength that is needed to attract the ink until a predetermined amount of ink (enough for the distal end portion of the needle in the slit to be immersed therein) is attracted from the ink storage means (usually an ink tank) into the slit is much higher than that for the production of an ink holding magnetic or electric field having such strength that is needed to keep the predetermined amount of ink in the slit.
In the prior art ink-dot printers, however, in ink attracting means keeps on producing a constant magnetic or electric field in the slit between the slit forming members during the time lapse which elapses from the instant that the ink starts to be attracted from the ink storage means into the slit until the ink in the slit starts to be returned to the ink storage means. Since the constant magnetic or electric field is the ink attracting magnetic or electric field, these prior art ink-dot printers require high power consumption.